Cancelled membership from PSA

Be very careful before becoming a member of PSA. I was a member for some time, cancelled my membership and they stopped collecting membership fees through Dept of Education. Then after a year or so, from nowhere, started deducting membershipfees on my payslip. After MANY struggles, they stopped for a year or so, and now in July 2017 for 3 months, deducted fees again. And there is no way how they refund their illegal deductions of membershipfees. BEWARE before joining this Union called PSA.